In the foregoing description of the muscles connected with the hyoid apparatus we have intentionally omitted those of the Giraffe, pre ferring, on account of the peculiar interest which the muscular arrangements of this ani mal present, to treat of them separately. We quote at length, therefore, from the accurate researches of Professor Owen.* " The mylo hyoideus is a thick and strong muscle , it arises from the whole of the internal surface of the lower jaw, and is inserted principally into the raphe, or longitudinal commissure, dividing it from its fellow of the opposite side. It adheres firmly to the genio-hyoideus : this arises by a well marked tendon from the posterior rugous surface of the symphysis menti, and has the usual insertion. The eenio-glossus arises by a tendon close to the inner side of the tendon of the genio-hyoideus ; its fleshy belly has a considerable antero posterior extent, and diminishes to a very thin edge at its anterior margin. The digas tricus has the usual origin, and is inserted, broad and thick, into the under side of the lower jaw. The stylo-hyoid is external to the digastricus, and is remarkable for the slender ness and length of its carneous part. The most interesting modifications in the muscles of the os *rides were found in those which retract that bone. The muscle which, as in some other ruminants, combines the offices of the sterno-thyroideus and sterno-hyoideus, arises in the Giraffe by a single long and slender carneous portion from the anterior extremity of the sternum ; this single fleshy origin is nine inches long, and terminates in a single round tendon, which is six inches long; the tendon then divides into two, and each di vision soon becomes fleshy, and so continues for about sixteen inches ; then each division again becomes tendinous for the extent of two inches, and ultimately carneous again, when it is inserted into the side of the thy roid cartilage, and is thence continued in the form of a fascia into the os hyoides. We have in this alternation of a contractile with a non contractile tissue a striking example of the use of tendon in limiting the length of the car neous or contractile part of a muscle to the extent of motion required to be produced in the part to which the muscle is attached. Had the sterno-thyroideus been continued fleshy as usual from its origin through the whole length of the neck to its insertion, it is obvious that a great proportion of the mus cular fibres would have been useless; for as these have the power of shortening themselves by their contractility only one-third of their own length, if they had been continued from end to end in the sterno-thyroidei, they would have been able to draw the larynx and os hyoides one-third of the way down the neck ; such displacement, however, is neither required nor indeed compatible with the me chanical connections of the parts ; but, by the intervention of long and slender tendons, the quantity of the contractile fibre is duly appor tioned to the extent of motion required for the lazynx and os hyoides. The muscle ana logous to the omo-hyoideus of other animals, is adjusted to its office by a different and more simple modification ; instead of having a remote origin from the shoulder-blade, its fixed point of attachment is brought forward to the nearest bone (the third cervical ver tebra) from which it could act upon the os hyoides with due power and extent of con traction. Its insertion is by a small round tendon." The muscles of the back and tail present few deviations worthy of remark. The spin alis and longissinzus dorsi exhibit the same attachments as in Solipeda. The sacro-lum balls is proportionately strong in ruminants. The semispinalis colli, according to the ob servations of Meckel, is very largely developed in the Camel, originating from the spinous apophyses as well as from the transverse processes of the five or six anterior dorsal vertebrm. These additional points of origin, while they afford a greater leverage power, constitute at the same time an important pe culiarity in this long-necked animal.
The diaphragm, which is present in all mam mifera, exhibits three openings for the passage of the aorta, cesophagus, and inferior vena cava. A very remarkable feature exists in connection with this muscle in the Camelidoe. It consists in the presence of a small bone situated near the margin of the central tendon. Meckel states that Dr. Jceger was the first to direct attention to this anomaly in the Dromedary and in the Vicugna*, the observation being subsequently confirmed by Dr. Leuckart and himself. In the two-humped or Bactrian Camel its presence was overlooked by the original discoverer, but afterwards ascertained by Meckel to oc cur in this species also. The bone offers slight variations according to the age of the individual ; it is thin and rather more than two inches long in the adult Camel ; in the Vicugna it is but feebly developed. Its so lidity is not acquired until a late period, for, in a Dromedary about two years old, the car tilaginous matrix only was discernible. In conclusion it may be said that this osseous formation is apparently designed to give sup port to the diaphragm, which is of great bulk in these animals.
Muscles of the shoulder and jitre-limb.—The trapezius has already been considered. The levator angulis srapulce (8, fig. 350.) varies little from the ordinary mammiferous type. The rhomboideus (9) is usually represented by two muscles, r. vzinor and r. nzajor ; the former, sornetimes called the superior, arises in the Sheep from the ligament= nuchm as far forward as the second vertebra of the neck, and the latter, or rhomboideus inferior, proceeds from the spines of the first two or three dor sal vertebrm, the fibres of both converging to be inserted into the upper border of the sca pula. In the Horse the muscle is single, and extends forward to the occiput, but is only connected superiorly to the cervical ligament. It is very feebly developed in the Camel, pass ing only from the spines of the two anterior dorsal vertebrm to the posterior angle of the scapula. In certain Pachydermata and in the Cetacea its appearance is still more insig nificant, but it is particularly large in the carnivorous mammals and in the Ornithorhyn chus. In the Giraffe it is inserted, like the largely developed serratus major, into the car tilage surrounding the base of the scapula; and in reference to the use of this structure Prof. Owen observes that " as the fore-part of the trunk is, as it were, slung upon the two great serrati muscles which principally support the weight of the remarkably deep chest of the Giraffe, the interposition of the elastic car tilages between the upper attachments of the muscles and the capitals of the bony columns of the two fore-legs, rnust be attended with the same advantage as is obtained by slinging the body of a coach upon elastic springs." * The serratzts nzagnus or nzajor (10,10) is ex ceedingly strong in this order. In quadrupeds generally, it differs from the human subject in presenting a cervical attachment in addition to its costal connection. In the Sheep it has no less than thirteen bundles of origin, eight of which come off' from a corresponding num ber of the superior ribs, the remaining five proceeding from the transverse apophyses of the third to the last cervical vertebra inclu sive. In other ruminants there is a slight numerical variation in regard to the fleshy digitations, but their general disposition is the same, being in all cases subsequently united and implanted into the base of the scapula, there forming, in conjunction with the tra pezius, a sling-like support to the anterior extremity. The serratus ntinor has an ar rangement in mammifera similar to that of its anologue, the lesser pectoral of the human subject ; but in the latter it is inserted into the coracoid apophysis of the scapula, while in the former it is usually connected to the humerus. In many carnivorous, edentate, and marsupial families this muscle is entirely wanting.